The present invention is related to systems and methods for electrical signal processing, and in particular to systems and methods for filtering electrical signals.
A variety of electrical signal filters and approaches for electrical signal filtering have been proposed and developed. For example, a known Tow-Thomas biquadratic filter 100 is depicted in FIG. 1. Filter 100 includes a lossy integrator, an inverting integrator and an inverting amplifier. The lossy integrator comprises an operational amplifier 120, a capacitor 114, and resistors 112, 116. This lossy integrator is used to achieve either low-pass or band-pass frequency states. The inverting integrator is formed of an operational amplifier 140, a resistor 132, and a capacitor 134. The inverting amplifier is formed of an operational amplifier 160 with resistors 152, 154 defining the gain. The inverting amplifier provides a low-noise pre-amplification for the entire circuit. The lossy integrator is coupled to the inverting amplifier via a feedback loop including a resistor 162. As shown, filter 100 provides a pair of complex poles, but requires three amplifiers to do so. In some cases, the inverting amplifier can be eliminated where the inverting integrator is modified to compensate. In this case, the filter requires one less amplifier to create a pair of complex poles. While the aforementioned circuits are capable of creating pairs of complex poles, the number of required amplifiers requires substantial die area and power consumption. Further, the preceding circuits utilize operational amplifiers which require more circuitry than other types of amplifiers.
Hence, for at least the aforementioned reasons, there exists a need in the art for advanced circuits and methods for creating complex pole pairs with reduced circuitry.